Coral death from sewage and phosphate pollution at Aqaba, Red Sea

Seawater samples were collected weekly over fourteen months at 25 m intervals between the surface and 200 m from the offshore waters of the Gulf of Aqaba, Red Sea. Water temperature and dissolved oxygen concentration and percent saturation were measured in situ. Within two hours of sampling, samples were analysed for chlorophyll a , ammonia, nitrate, nitrite, phosphate and silicate. The temperature field depicted a well defined seasonal pattern of winter mixing from December to April and summer stratification from May to November. All other analysed parameters were intimately related to this pattern. Dissolved oxygen showed a maximum and homogeneous distribution in winter and a minimum in summer. Chlorophyll a showed a seasonal pattern close to that of dissolved oxygen, but with a distinct summer peak between 50 and 75 m. Ammonia was absent from the entire water column during summer and relatively abundant and homogeneously distributed in winter. Nitrite had a seasonal pattern similar to that of chlorophy...

Dissolved Oxygen, Chlorophyll a and Nutrients: Seasonal Cycles in Waters of the Gulf of Aquaba, Red Sea

Calcification rates in different fragments along branches of the hermatypic coral Stylophora pistillata were tested in the laboratory using a new technique, the “optic glassfiber” method. By this method, the tested colony remains constantly in dark conditions while a narrow beam of light, transferred through the optic fiber, illuminates a small distinct point of coral tissue (on a branch tip or base). The selected illuminated portion of the branch serves as the experimental fragment, while all the other parts of the same colony serve as the dark controls. The results indicate that significantly more calcium is incorporated in the tip fragments than in the bases, both in light and in dark conditions (4.1 to 13.2 times more). Illumination of the tips or the bases did not stimulate or enhance the calcification rates of these fragments. Thus, in all colonies tested, the calcification rates of the illuminated fragments were not significantly different from the average rates of other similar, non-illuminated fragments of the same colony. It is suggested that light does not directly enhance calcification in hermatypic corals, but rather, that light enhances O2 production, which consequently stimulates coral metabolism. Our preliminary results indicate that calcification rates recorded in aerated dark experiments are significantly higher than calcification rates of non-aerated dark controls.

Does light enhance calcification in hermatypic corals

Records of long term (14 months) fine temporal resolution (weekly) monitoring of the ambient water temperature, dissolved oxygen concentration and percent saturation, the inorganic nutrients ammonia, nitrate, nitrite, phosphate and silicate and chlorophyll a concentrations were generated to assess sea water quality within the Jordanian coast of the Gulf of Aqaba. Surface water (1 m) samples were collected from four coastal stations, contrasting in their natural benthic habitats and adjacent human activities. Offshore surface water was also concurrently sampled at two locations. The offshore stations were reference sites. Modifications in the coastal water quality were assessed as the difference between the magnitude of a specific parameter recorded at a coastal station and the concurrently recorded value of the parameter at the reference offshore station, relative to the annual mean value at the reference offshore station. A sandy beach-sea grass bed habitat was found to have significantly positi...

N. Hulings

Papers

Calcium and phosphate in the Jordan Gulf of Aqaba